Fish Biomass and Community Structure Around Standing and Toppled Oil and Gas Platforms in the Northern Gulf of Mexico Using Hydroacoustic and Video Surveys

There has been relatively little study of the efficacy of decommissioned oil and gas platforms as artificial reef habitats for fish assemblages in the northern Gulf of Mexico (GOM). A variety of fish species have been reported on these structures, but the species biomass distribution and community structure has not been studied thoroughly. Hydroacoustic and video surveys were conducted quarterly from June 2013 to June 2014 at three standing and two toppled oil and gas platforms located approximately 130 km off the coast of Louisiana at 90 m depth; to gain information about the spatial biomass distribution and community structure at standing and toppled platforms. The toppled platforms in our study became a part of the Louisiana Artificial Reef Program in 2002. Stereo and Go-Pro® cameras were utilized for video surveys, allowing us to record counts and lengths of fishes. Hydroacoustic surveys were used to define the spatial distribution of fish biomass (MVBS, SV) in relation to distance to 500 m from the center of each site and the depth distribution of the observed biomass. MVBS of fishes was highest when near the structure and declined rapidly as distance from the structure increased, leveling off to a background-noise level at 100 m from the structure. Additionally, fish MVBS was highest in the lower water column (\u3e60 m) compared to the upper and middle water columns. The fish communities differed between depth layers in the water column, seasonally, and between structure types (standing/toppled), with red snapper (Lutjanus campechanus) as a dominant species present at both site types. Coupling the data from these methods revealed that even though fish MVBS remained consistent throughout all seasons, different species comprise the MVBS observed during different seasons and between different layers in the water column. Coupling non-destructive methods allows for rapid monitoring which can be helpful in determining how to effectively manage both the fishes around the structure and the structures themselves